The Capasso Group have designed a device that converts an arbitrary spin state of light into a total angular momen- tum state (OAM) characterized by a superposition of two independent OAM states. They experimentally demonstrate this for a device that converts left- and right-circularly polarized light into helical beams with independent values of OAM and for a second device that performs the same operation for orthogonal elliptical polarizations.

There are several applications that can be easily foreseen for this device, some examples include:

1. In telecommunications – a constant effort from research groups is to encode as much information as possible in a single photon. Angular momentum of light is one such tunable parameter. This device makes possible new combinations of photon pairs that can be used in secure data transmission.
2. Structured light – helical modes of light carrying orbital angular momentum have non-trivial field distributions (structured light) when focused by a high numerical aperture lens. This can be used for lithography applications, optical manipulation of micro-objects in Optical Tweezers and ultramicroscopy like STED microscopy.
3. New lasers – the device can be used to build lasers that emit light carrying orbital angular momentum, directly ready for applications of points 1) and 2).

This work was published in Science.